Final answer:
The assertion that a straight-chain alkene has a higher boiling point than a branched-chain alkane is incorrect; the boiling points of alkenes and alkanes with similar molar masses are usually quite close to each other.
Step-by-step explanation:
The assertion that a straight-chain alkene has a higher boiling point than a branched-chain alkane is incorrect. Boiling points in organic compounds generally increase with increasing molar mass due to greater surface area and interaction strength. However, for molecules with the same number of carbons, the difference in boiling points is usually minimal. Structures also play a role, as branched alkanes can have lower boiling points than their straight-chain isomers due to lower surface area and weaker London dispersion forces.
Therefore, alkenes and alkanes with similar molar masses will have similar boiling points, and any variation could depend on the branching and molecular shape. However, both types of compounds typically have lower boiling points than substances capable of stronger intermolecular interactions, like alcohols, which engage in hydrogen bonding. The reason given in the assertion seems to apply more to differences between families of organic compounds, such as alkanes versus alcohols, and has been inaccurately generalized to the alkene-alkane comparison.